Linux UART 开发指南

linux4.9
|-- drivers
|     |-- tty
|     |    |-- serial
|     |    |-- serial_core.c
|     |    |-- sunxi-uart.c
|     |    |-- sunxi-uart.h

linux-4.9
board.dts
|--------sun*.dtsi
			|------sun*-pinctrl.dtsi
			|------sun*-clk.dtsi
linux-5.4
board.dts
|-------sun*.dtsi

/ {
    model = "sun*";
    compatible = "arm,sun*";
    interrupt-parent = <&wakeupgen>;
    #address-cells = <2>;
    #size-cells = <2>;
    aliases {
        serial0 = &uart0;
        serial1 = &uart1;
        serial2 = &uart2;
        serial3 = &uart3;
        serial4 = &uart4;
        serial5 = &uart5;
        ...
    };

    uart0: uart@05000000 {
        compatible = "allwinner,sun50i-uart"; /* 用于驱动和设备绑定 */
        device_type = "uart0";                /* 设备类型*/
        reg = <0x0 0x05000000 0x0 0x400>;     /* 设备使用的寄存器基地址以及范围*/
        interrupts = <GIC_SPI 0 IRQ_TYPE_LEVEL_HIGH>; /* 设备使用的硬件中断号*/
        clocks = <&clk_uart0>;                /* 设备使用的时钟*/
        pinctrl-names = "default", "sleep";
        pinctrl-0 = <&uart0_pins_a>;          /* 设备正常状态下使用的pin脚*/
        pinctrl-1 = <&uart0_pins_b>;          /* 设备休眠状态下使用的pin脚*/
        uart0_port = <0>; /* uart控制器对应的ttyS唯一端口号，不能与其他uart控制器重复*/
        uart0_type = <2>; /* uart控制器线数，取值2/4/8*/
        use_dma = <0>;    /* 是否采用DMA 方式传输，0：不启用，1：只启用TX，2：只启用RX，3：启 用TX 与RX*/
        status = "okay"; /* 是否使能该节点*/
};

uart0: uart@5000000 {
    compatible = "allwinner,sun50i-uart";
    device_type = "uart0";
    reg = <0x0 0x05000000 0x0 0x400>;
    interrupts = <GIC_SPI 0 IRQ_TYPE_LEVEL_HIGH>;
    sunxi,uart-fifosize = <64>;
    clocks = <&ccu CLK_BUS_UART0>; /* 设备使用的时钟 */
    clock-names = "uart0";
    resets = <&ccu RST_BUS_UART0>; /* 设备reset时钟 */
    pinctrl-names = "default", "sleep";
    pinctrl-0 = <&uart0_pins_a>;
    pinctrl-1 = <&uart0_pins_b>;
    uart0_port = <0>;
    uart0_type = <2>;
    dmas = <&dma 14>; /* 14表示DRQ */
    dma-names = "tx";
    use_dma = <0>; /* 是否采用DMA 方式传输，0：不启用，1：只启用TX，2：只启用RX，3：启用TX 与RX */
};

soc@03000000 {
    ...
    &uart0 {
        uart-supply = <reg_dcdc1>; /* IO使用的电 */
        status = "okay";
    };

    &uart1 {
        status = "okay";
    };
    ...
}

uart1: uart@05000400 {
    ...
    use_dma = <3>; /* 是否采用DMA 方式传输，0：不启用，1：只启用TX，2：只启用RX，3：启用TX 与RX */
    status = "okay";
};

uart0: uart@5000000 {
    ...
    dmas = <&dma 14>; /* 14表示DRQ, 查看dma spec */
    dma-names = "tx";
    use_dma = <0>; /* 是否采用DMA 方式传输，0：不启用，1：只启用TX，2：只启用RX，3：启用TX 与RX
    */
};

uart1: uart@05000400 {
    compatible = "allwinner,sun50i-uart";
    device_type = "uart1";
    reg = <0x0 0x05000400 0x0 0x400>;
    interrupts = <GIC_SPI 1 IRQ_TYPE_LEVEL_HIGH>;
    clocks = <&clk_uart1>;
    pinctrl-names = "default", "sleep";
    pinctrl-0 = <&uart1_pins_a>;
    pinctrl-1 = <&uart1_pins_b>;
    uart1_port = <1>;
    uart1_type = <4>;
    status = "okay"; /* 确保该uart已经使能 */
};

console=ttyS1,115200
说明:
ttyS0 <===> uart0
ttyS1 <===> uart1
...

#define B4800 0000014
#define B9600 0000015
#define B19200 0000016
#define B38400 0000017
#define B57600 0010001
#define B115200 0010002
#define B230400 0010003
#define B460800 0010004
#define B500000 0010005
#define B576000 0010006
#define B921600 0010007
#define B1000000 0010010
#define B1152000 0010011
#define B1500000 0010012
#define B2000000 0010013
#define B2500000 0010014
#define B3000000 0010015
#define B3500000 0010016
#define B4000000 0010017

    device_type = "uart2";
    reg = <0x0 0x05000800 0x0 0x400>;
    interrupts = <GIC_SPI 2 IRQ_TYPE_LEVEL_HIGH>;
- 	clocks = <&clk_uart2>;
+ 	clocks = <&clk_uart2>, <&clk_apb2>, <&clk_psi>;
+ 	clock-frequency = <50000000>;
	pinctrl-names = "default", "sleep";

	device_type = "uart0";
	reg = <0x0 0x05000000 0x0 0x400>;
	interrupts = <GIC_SPI 0 IRQ_TYPE_LEVEL_HIGH>;
- 	clocks = <&clk_uart0>;
+	clocks = <&clk_uart0>, <&clk_apb2>, <&clk_psi>;
+ 	clock-frequency = <50000000>;
	pinctrl-names = "default", "sleep";

	device_type = "uart2";
	reg = <0x0 0x05000800 0x0 0x400>;
	interrupts = <GIC_SPI 2 IRQ_TYPE_LEVEL_HIGH>;
- 		clocks = <&clk_uart2>;
+ 		clocks = <&ccu CLK_BUS_UART0>,
+ 				 <&ccu CLK_APB2>,
+ 				 <&ccu CLK_PSI_AHB1_AHB2>;
+ 		clock-frequency = <50000000>;
	pinctrl-names = "default", "sleep";

/ {
	soc@03000000{
		r_pio: pinctrl@07022000 {
			...
			/* 配置CPUS域uart pin信息 */
			s_uart0_pins_a: s_uart0@0 {
                allwinner,pins = "PL2", "PL3";
                allwinner,function = "s_uart0";
                allwinner,muxsel = <2>;
                allwinner,drive = <1>;
                allwinner,pull = <1>;
			};
			...
		};
	...
};	

clk_suart0: suart0 {
    #clock-cells = <0>;
    compatible = "allwinner,periph-cpus-clock";
    clock-output-names = "suart0";
};

aliases {
    serial0 = &uart0;
    ...
    serial5 = &uart5; //添加uart5的别名，必须要添加
};
uart0:uart@05000000 {
};
....
/* 添加uart控制器信息 ，必须要添加，具体属性含义，见上文 */
uart5: uart@07080000 {
    compatible = "allwinner,sun8i-uart";
    device_type = "uart5";
    reg = <0x0 0x07080000 0x0 0x400>;
    interrupts = <GIC_SPI 111 IRQ_TYPE_LEVEL_HIGH>;
    clocks = <&clk_suart0>;
    pinctrl-names = "default", "sleep";
    pinctrl-1 = <&s_uart0_pins_a>;
    uart5_port = <5>;
    uart5_type = <2>;
    status = "okay";
};

static const struct sunxi_desc_pin *_r_pins[] = {
    SUNXI_PIN(SUNXI_PINCTRL_PIN(L, 0),
    ...
    SUNXI_PIN(SUNXI_PINCTRL_PIN(L, 2),
    ...
    SUNXI_FUNCTION(0x2, "s_uart0"), //没有则要添加
    ...
    SUNXI_PIN(SUNXI_PINCTRL_PIN(L, 3),
    ...
    SUNXI_FUNCTION(0x2, "s_uart0"), //没有则要添加
    ...
};

/* clk-*.h */
#define CPUS_UART_GATE 0x018C

/* clk-*.c */
static const char *suart_parents[] = {"cpurapbs2"};

SUNXI_CLK_PERIPH(suart0, 0, 0, 0, 0,
                0, 0, 0, 0, 0, 0,
                CPUS_UART_GATE, CPUS_UART_GATE, 0, 0, 16, 0,
                0, &clk_lock, NULL, 0);
                
struct periph_init_data sunxi_periphs_cpus_init[] = {
    ...
    {"suart0", 0, suart_parents,
    ARRAY_SIZE(suart_parents), &sunxi_clk_periph_suart0 },
};

int open(const char *pathname, int flags);
int close(int fd);

#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <unistd.h>

ssize_t read(int fd, void *buf, size_t count);
ssize_t write(int fd, const void *buf, size_t count);

#include <unistd.h>

#define NCCS 19
struct termios {
    tcflag_t c_iflag;  /* input mode flags */
    tcflag_t c_oflag;  /* output mode flags */
    tcflag_t c_cflag;  /* control mode flags */
    tcflag_t c_lflag;  /* local mode flags */
    cc_t c_line;       /* line discipline */
    cc_t c_cc[NCCS];   /* control characters */
};

#include <stdio.h>      /*标准输入输出定义*/
#include <stdlib.h>     /*标准函数库定义*/
#include <unistd.h>     /*Unix 标准函数定义*/
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>       /*文件控制定义*/
#include <termios.h>     /*PPSIX 终端控制定义*/
#include <errno.h>       /*错误号定义*/
#include <string.h>

enum parameter_type {
    PT_PROGRAM_NAME = 0,
    PT_DEV_NAME,
    PT_CYCLE,
    PT_NUM
};
 
#define DBG(string, args...) \
    do { \
        printf("%s, %s()%u---", __FILE__, __FUNCTION__, __LINE__); \
        printf(string, _00args); \
        printf("\n"); \
    } while (0)

void usage(void)
{
    printf("You should input as: \n");
    printf("\t select_test [/dev/name] [Cycle Cnt]\n");
}

int OpenDev(char *name)
{
    int fd = open(name, O_RDWR ); //| O_NOCTTY | O_NDELAY
    if (-1 == fd)
	    DBG("Can't Open(%s)!", name);

    return fd;
}

/**
 * @brief 设置串口通信速率
 * @param fd 类型 int 打开串口的文件句柄
 * @param speed 类型 int 串口速度
 * @return void
 */
void set_speed(int fd, int speed)
{
    int i;
    int status;
    struct termios Opt = {0};
    int speed_arr[] = { B38400, B19200, B9600, B4800, B2400, B1200, B300,
    	B38400, B19200, B9600, B4800, B2400, B1200, B300, };
    int name_arr[] = {38400, 19200, 9600, 4800, 2400, 1200, 300, 38400,
    	19200, 9600, 4800, 2400, 1200, 300, };

    tcgetattr(fd, &Opt);

    for ( i= 0; i < sizeof(speed_arr) / sizeof(int); i++) {
        if (speed == name_arr[i])
        break;
    }

    tcflush(fd, TCIOFLUSH);
    cfsetispeed(&Opt, speed_arr[i]);
    cfsetospeed(&Opt, speed_arr[i]);

    Opt.c_lflag &= ~(ICANON | ECHO | ECHOE | ISIG); /*Input*/
    Opt.c_oflag &= ~OPOST; /*Output*/

    status = tcsetattr(fd, TCSANOW, &Opt);
    if (status != 0) {
        DBG("tcsetattr fd");
        return;
    }
    tcflush(fd, TCIOFLUSH);
}

/**
 *@brief 设置串口数据位，停止位和效验位
 *@param fd 类型 int 打开的串口文件句柄
 *@param databits 类型 int 数据位 取值 为 7 或者8
 *@param stopbits 类型 int 停止位 取值为 1 或者2
 *@param parity 类型 int 效验类型 取值为N,E,O,,S
 */
int set_Parity(int fd,int databits,int stopbits,int parity)
{
    struct termios options;

    if ( tcgetattr(fd, &options) != 0) {
        perror("SetupSerial 1");
        return -1;
    }
    options.c_cflag &= ~CSIZE;

    switch (databits) /*设置数据位数*/
    {
        case 7:
            options.c_cflag |= CS7;
            break;
        case 8:
            options.c_cflag |= CS8;
            break;
        default:
            fprintf(stderr,"Unsupported data size\n");
            return -1;
    }
    
    switch (parity)
    {
        case 'n':
        case 'N':
            options.c_cflag &= ~PARENB; /* Clear parity enable */
            options.c_iflag &= ~INPCK; /* Enable parity checking */
            break;
        case 'o':
        case 'O':
            options.c_cflag |= (PARODD | PARENB); /* 设置为奇效验*/
            options.c_iflag |= INPCK; /* Disnable parity checking */
            break;
        case 'e':
        case 'E':
            options.c_cflag |= PARENB; /* Enable parity */
            options.c_cflag &= ~PARODD; /* 转换为偶效验*/
            options.c_iflag |= INPCK; /* Disnable parity checking */
            break;
        case 'S':
        case 's': /*as no parity*/
            options.c_cflag &= ~PARENB;
            options.c_cflag &= ~CSTOPB;break;
        default:
            fprintf(stderr,"Unsupported parity\n");
            return -1;
    }
    
    /* 设置停止位*/
    switch (stopbits)
    {
        case 1:
            options.c_cflag &= ~CSTOPB;
            break;
        case 2:
            options.c_cflag |= CSTOPB;
            break;
        default:
            fprintf(stderr,"Unsupported stop bits\n");
            return -1;
    }
    
    /* Set input parity option */
    if (parity != 'n')
    	options.c_iflag |= INPCK;
    tcflush(fd,TCIFLUSH);
    options.c_cc[VTIME] = 150; /* 设置超时15 seconds*/
    options.c_cc[VMIN] = 0;    /* Update the options and do it NOW */
    if (tcsetattr(fd,TCSANOW,&options) != 0)
    {
        perror("SetupSerial 3");
        return -1;
    }
    return 0;
}

void str_print(char *buf, int len)
{
    int i;

    for (i=0; i<len; i++) {
        if (i%10 == 0)
            printf("\n");

        printf("0x%02x ", buf[i]);
    }
    printf("\n");
}

int main(int argc, char **argv)
{
    int i = 0;
    int fd = 0;
    int cnt = 0;
    char buf[256];

    int ret;
    fd_set rd_fdset;
    struct timeval dly_tm; // delay time in select()

    if (argc != PT_NUM) {
        usage();
        return -1;
    }

    sscanf(argv[PT_CYCLE], "%d", &cnt);
    if (cnt == 0)
        cnt = 0xFFFF;

    fd = OpenDev(argv[PT_DEV_NAME]);
    if (fd < 0)
        return -1;

    set_speed(fd,19200);
    if (set_Parity(fd,8,1,'N') == -1) {
        printf("Set Parity Error\n");
        exit (0);
    }

    printf("Select(%s), Cnt %d. \n", argv[PT_DEV_NAME], cnt);
    while (i<cnt) {
        FD_ZERO(&rd_fdset);
        FD_SET(fd, &rd_fdset);

        dly_tm.tv_sec = 5;
        dly_tm.tv_usec = 0;
        memset(buf, 0, 256);

        ret = select(fd+1, &rd_fdset, NULL, NULL, &dly_tm);
        // DBG("select() return %d, fd = %d", ret, fd);
        if (ret == 0)
            continue;

        if (ret < 0) {
            printf("select(%s) return %d. [%d]: %s \n", argv[PT_DEV_NAME], ret, errno,
            strerror(errno));
            continue;
        }

        i++;
        ret = read(fd, buf, 256);

        printf("Cnt%d: read(%s) return %d.\n", i, argv[PT_DEV_NAME], ret);
        str_print(buf, ret);
    }

    close(fd);
    return 0;
}

1.挂载debugfs。 
mount -t debugfs none /sys/kernel/debug
2.打开uart模块所有打印。
echo "module sunxi_uart +p" > /mnt/dynamic_debug/control
3.打开指定文件的所有打印。
echo "file sunxi-uart.c +p" > /mnt/dynamic_debug/control
4.打开指定文件指定行的打印。
echo "file sunxi-uart.c line 615 +p" > /mnt/dynamic_debug/control
5.打开指定函数名的打印。
echo "func sw_uart_set_termios +p" > /mnt/dynamic_debug/control
6.关闭打印。
把上面相应命令中的+p 修改为-p 即可。
更多信息可参考linux 内核文档：linux-3.10/Documentation/dynamic-debug-howto.txt。

1.定义CONFIG_SERIAL_DEBUG宏。
linux-4.9 内核版本中默认没有定义CONFIG_SERIAL_DEBUG ， 需要自行在
drivers/tty/serial/Kconfig 中添加CONFIG_SERIAL_DEBUG 定义，然后drivers/tty/serial/Makefile文件中添加代码ccflags-$(CONFIG_SERIAL_DEBUG) := -DDEBUG。 
注：使用该宏，需要内核关闭CONFIG_DYNAMIC_DEBUG宏。

1./sys/devices/platform/soc/uart0/dev_info

cupid-p2:/ # cat /sys/devices/platform/soc/uart0/dev_info
id = 0
name = uart0
irq = 247
io_num = 2
port->mapbase = 0x0000000005000000
port->membase = 0xffffff800b005000
port->iobase = 0x00000000
pdata->regulator = 0x (null)
pdata->regulator_id =

从该节点可以看到uart端口的一些硬件资源信息。

2./sys/devices/platform/soc/uart0/ctrl_info
cupid-p2:/ # cat /sys/devices/platform/soc/uart0/ctrl_info
ier : 0x05
lcr : 0x13
mcr : 0x03
fcr : 0xb1
dll : 0x0d
dlh : 0x00
last baud : 115384 (dl = 13)

TxRx Statistics:
tx : 61123
rx : 351
parity : 0
frame : 0
overrun: 0

此节点可以打印出软件中保存的一些控制信息，如当前UART 端口的寄存器值、收发数据的统计等。

3./sys/devices/platform/soc/uart0/status
cupid-p2:/ # cat /sys/devices/platform/soc/uart0/status
uartclk = 24000000
The Uart controller register[Base: 0xffffff800b005000]:
[RTX] 0x00 = 0x0000000d, [IER] 0x04 = 0x00000005, [FCR] 0x08 = 0x000000c1
[LCR] 0x0c = 0x00000013, [MCR] 0x10 = 0x00000003, [LSR] 0x14 = 0x00000060
[MSR] 0x18 = 0x00000000, [SCH] 0x1c = 0x00000000, [USR] 0x7c = 0x00000006
[TFL] 0x80 = 0x00000000, [RFL] 0x84 = 0x00000000, [HALT] 0xa4 = 0x00000002

此节点可以打印出当前UART 端口的一些运行状态信息，包括控制器的各寄存器值。